Image sensor and imaging apparatus

ABSTRACT

An image sensor is provided, the image sensor including: an imaging unit that has a first imaging region and a second imaging region, and outputs: a first pixel signal generated according to light incident on the first imaging region; and a second pixel signal generated according to light incident on the second imaging region; a first ramp generating unit that generates a first ramp signal; a second ramp generating unit that generates a second ramp signal; a first signal converting unit that converts the first pixel signal into a first digital image signal based on a result of comparison between the first pixel signal and the first ramp signal; and a second signal converting unit that converts the second pixel signal into a second digital image signal based on a result of comparison between the second pixel signal and the second ramp signal.

This is a Continuation of application Ser. No. 15/261,049, filed Sep. 9,2016 which is a Continuation of application Ser. No. 15/102,238 filedSep. 9, 2016, which in turn is a National Stage Application ofPCT/JP2014/081791 filed Dec. 1, 2014, which claims the benefit ofJapanese Patent Application No. 2013-252940, filed Dec. 6, 2013. Theentire disclosures of the prior applications are hereby incorporated byreference herein in their entirety.

BACKGROUND 1. Technical Field

The present invention relates to an image sensor and an imagingapparatus.

2. Related Art

Conventionally, an imaging apparatus comprising, as AD converters thatconvert signals from a CMOS image sensor or the like into digitalsignals, a plurality of AD converters that use ramp waveforms (see forexample, Patent document 1).

Patent document 1: Japanese Patent Application Publication No.2006-303752

Because common ramp waveforms are input to the plurality of ADconverters, it has been difficult to independently adjustcharacteristics such as gains for the respective AD converters.

SUMMARY

Therefore, it is an object of an aspect of the innovations herein toprovide an image sensor and an imaging apparatus, which are capable ofovercoming the above drawbacks accompanying the related art. The aboveand other objects can be achieved by combinations described in theclaims. That is, a first aspect of the present invention provides animage sensor comprising: a plurality of signal lines that read outrespective signals light-received by a plurality of light-receivingunits that are among a plurality of light-receiving units and arearranged in a first direction; and a control unit that reads out thesignals with a difference being generated in timing at which a signal isread out through one signal line among the plurality of signal lines andtiming at which a signal is read out through another signal line.

A second aspect of the present invention provides an image sensorcomprising: an imaging unit that has a first imaging region and a secondimaging region, and outputs: a first pixel signal generated according tolight incident on the first imaging region; and a second pixel signalgenerated according to light incident on the second imaging region; afirst ramp generating unit that generates a first ramp signal; a secondramp generating unit that generates a second ramp signal; a first signalconverting unit that converts the first pixel signal into a firstdigital image signal based on a result of comparison between the firstpixel signal and the first ramp signal; and a second signal convertingunit that converts the second pixel signal into a second digital imagesignal based on a result of comparison between the second pixel signaland the second ramp signal.

A third aspect of the present invention provides an imaging apparatuscomprising the image sensor according to the first or second aspect.

The summary clause does not necessarily describe all necessary featuresof the embodiments of the present invention. The present invention mayalso be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a figure showing one example of the configuration of an imagesensor 100 according to an embodiment of the present invention.

FIG. 2 is a figure showing a configuration example of an imaging region131 and an AD converting unit 180.

FIG. 3 is a timing diagram showing an operation example of a firstimaging region 131-1 and a second imaging region 131-2.

FIG. 4 is a figure showing an example of a plurality of the imagingregions 131.

FIG. 5 is a figure showing another example of the plurality of imagingregions 131.

FIG. 6 is a figure showing another example of the plurality of imagingregions 131.

FIG. 7 is a figure showing a configuration example of an imaging unit120 and a plurality of the AD converting units 180.

FIG. 8 is a timing diagram showing an operation example of four ADconverting units 180 provided in the same column.

FIG. 9 is a timing diagram showing details of an operation of a first ADconverting unit 180-1 and a second AD converting unit 180-2 in theoperation example shown in FIG. 8.

FIG. 10 is a timing diagram showing another operation example of four ADconverting units 180 provided in the same column.

FIG. 11 is a timing diagram showing details of an operation of the firstAD converting unit 180-1 and a third AD converting unit 180-3 in theoperation example shown in FIG. 10.

FIG. 12 is a figure showing an image of differences in the timing ofreadout in rolling readout.

FIG. 13A is a figure showing a configuration example of a plurality oframp generating units 182.

FIG. 13B is a figure showing another configuration example of theplurality of ramp generating units 182.

FIG. 14 is a cross-sectional view of the image sensor 100 according tothe present embodiment.

FIG. 15 is a block diagram showing a configuration example of an imagingapparatus 500 according to an implementation example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The embodiments do not limit the invention according to the claims, andall the combinations of the features described in the embodiments arenot necessarily essential to means provided by aspects of the invention.

FIG. 1 is a figure showing one example of the configuration of an imagesensor 100 according to an embodiment of the present invention. Theimage sensor 100 is, for example, a camera that captures a still imageor moving image. The image sensor 100 according to the present examplecomprises an imaging unit 120, a plurality of AD converting units 180and a plurality of ramp generating units 182.

The imaging unit 120 has a plurality of imaging regions 131. Therespective imaging regions 131 store electrical charges according toincident light. the respective imaging regions 131 have one or morephotoelectric converting units that convert incident light intoelectrical charges and store the electrical charges. The photoelectricconverting units are one example of light-receiving units. the imagesensor 100 generates pixel signals according to incident light byreading out the amounts of electrical charges stored by the respectiveimaging regions 131. In FIG. 1, a first imaging region 131-1 thatgenerates a first pixel signal and a second imaging region 131-2 thatgenerates a second pixel signal are shown.

The first imaging region 131-1 has one or more first photoelectricconverting units, and the second imaging region 131-2 has one or moresecond photoelectric converting units. For example, the imaging unit 120has a plurality of photoelectric converting units arranged in a matrixform, and the respective imaging regions 131 may include one column ofphotoelectric converting units. Also, an imaging region 131 may includediscretely arranged photoelectric converting units. Also, an imagingregion 131 may be a block having predetermined lengths (the numbers ofphotoelectric converting units) in the row direction and the columndirection. Also, among a plurality of photoelectric converting unitsarranged in a first direction (for example, a plurality of photoelectricconverting unit included in a predetermined row or column), somephotoelectric converting units may be included in the first imagingregion 131-1, and some other photoelectric converting units may beincluded in the second imaging region 131-2. Signal lines that read outsignals according to received light are connected to respectivephotoelectric converting units.

The AD converting units 180 are provided corresponding to the respectiveimaging regions 131. In FIG. 1, a first AD converting unit 180-1 and asecond AD converting unit 180-2 corresponding to the first imagingregion 131-1 and the second imaging region 131-2 are shown. Therespective AD converting units 180 are one example of signal convertingunits that convert, into digital image signals, analog pixel signalsaccording to the amounts of electrical charges stored in therespectively corresponding imaging regions 131. The first AD convertingunit 180-1 converts a first pixel signal into a first digital imagesignal, and the second AD converting unit 180-2 converts a second pixelsignal into a second digital image signal. Also, if a plurality ofphotoelectric converting units is included in an imaging region 131, andAD converting unit 180 may sequentially read out analog signalsgenerated by the plurality of photoelectric converting units accordingto the amounts of electrical charges, and convert the analog signalsinto digital image signals. The AD converting units 180 function assignal converting units that convert, into digital signals, signals readout from photoelectric converting units for each of a plurality ofsignal lines connected to a plurality of photoelectric converting units.

At least two ramp generating units 182 are provided. In FIG. 1, a firstramp generating unit 182-1 and a second ramp generating unit 182-2provided corresponding to the first AD converting unit 180-1 and thesecond AD converting unit 180-2 are shown. The respective rampgenerating units 182 generate ramp signals. The characteristics of theramp signals, such as inclinations, that are generated by the respectiveramp generating units 182 are independently controllable for each of theramp generating units 182. The ramp generating units 182 may be providedin a one-to-one correspondence with the plurality of AD converting units180, and at least some of the ramp generating units 182 may be shared bytwo or more AD converting units 180.

A ramp generating unit 182 functions as a control unit that controlstiming at which a signal is read out through a signal line connected toa photoelectric converting unit. The ramp generating units 182 accordingto the present example control timing of signal conversion at therespectively corresponding AD converting units 180. The control unit cangenerate a difference in timing at which a signal is read out throughone signal line among a plurality of signal lines and timing at which asignal is read out through another signal line. In one example, thecontrol unit can generate a difference in timing at which a signal isread out through each of a plurality of signal lines. In this case, aramp generating unit 182 may be provided to each of the plurality ofsignal lines.

The respective AD converting units 180 convert pixel signals intodigital signals based on a result of comparison between ramp signalsgenerated by corresponding ramp generating units 182 and correspondingpixel signals. For example, an AD converting unit 180 converts the levelof a pixel signal into a digital value by outputting the digital valueaccording to a length of time from timing at which a ramp signal isreceived to timing at which the level of the ramp signal crosses thelevel of the pixel signal.

Because the image sensor 100 according to the present example comprisesthe plurality of ramp generating units 182, ramp signals with differentcharacteristics can be used for each of the imaging regions 131. Forexample, by using ramp signals with inclinations that are different forthe first imaging region 131-1 and the second imaging region 131-2, thegains of the digital values of digital image signals relative to theanalog levels of pixel signals output by the imaging regions 131 can bemade different. Also, by using ramp signals generated at differenttiming for the first imaging region 131-1 and the second imaging region131-2, timing at which pixel signals output by the imaging regions 131are read out can be made different from each other. That is, pixelsignals can be read out with a difference being generated in timing atwhich a pixel signal is read out through one signal line among aplurality of signal lines and timing at which a pixel signal is read outthrough another signal line. By causing the pixel signals to be read outwith a difference being generated between signal lines in timing atwhich pixel signals are read out through the signal lines, the controlunit including the ramp generating units 182 may read out, while a firstphotoelectric converting unit among a plurality of photoelectricconverting units is receiving light, a pixel signal received by a secondphotoelectric converting unit among the plurality of photoelectricconverting units.

FIG. 2 is a figure showing a configuration example of an imaging region131 and an AD converting unit 180. In the present example, an imagingunit 120 including a plurality of imaging regions 131 is provided in animaging chip 113. Also, a plurality of AD converting units 180 and aplurality of ramp generating units 182 are provided in a signalprocessing chip 111. In FIG. 2, a set of an imaging region 131, an ADconverting unit 180 and a plurality of ramp generating units 182 isshown.

The imaging chip 113 and the signal processing chip 111 aresemiconductor chips, for example. The signal processing chip 111 isstacked on the imaging chip 113. For example, the signal processing chip111 is arranged to overlap the imaging chip 113, and is electricallyconnected with the imaging chip 113 via a bump 109 or the like. In thismanner, the imaging unit 120, and the AD converting unit 180 and theramp generating unit 182 are provided on separate chips so that theplurality of AD converting units 180 and the plurality of rampgenerating units 182 can be provided easily while suppressing increasein the area of the imaging unit 120. Also, wire lengths between therespective photoelectric converting units 104 and AD converting units180 can be made short, and pixel signals can be read out precisely.

The imaging region 131 has a single photoelectric converting unit 104, atransfer transistor 152, a reset transistor 154, an amplificationtransistor 156 and a selection transistor 158. The source and drain ofthe transfer transistor 152 are connected to the output terminal of thephotoelectric converting unit 104 and the gate of the amplificationtransistor 156, respectively. The parasitic capacitance of a wirebetween the output terminal of the photoelectric converting unit 104 andthe source of the transfer transistor 152 functions as an electricalcharge storing unit that stores electrical charges generated by thephotoelectric converting unit 104. The electrical charge storing unit inthe present example is part of the photoelectric converting unit 104.The gate of the transfer transistor 152 receives a transfer signal Txfor controlling whether or not to transfer the amount of electricalcharges stored by the electrical charge storing unit.

The drain of the reset transistor 154 receives a reference voltage VDD,and its source is connected to the gate of the amplification transistor156. The gate of the reset transistor 154 receives a reset signal Resetfor controlling whether or not to reset the amount of electrical chargesstored by the electrical charge storing unit.

The drain of the amplification transistor 156 receives the referencevoltage VDD, and its source is connected to the drain of the selectiontransistor 158. The amplification transistor 156 outputs an analog pixelsignal according to the amount of electrical charges transferred fromthe transfer transistor 152. The gate of the selection transistor 158receives a selection signal Select, and its source is connected to theAD converting unit 180. The selection transistor 158 inputs a pixelsignal from the transfer transistor 152 to the AD converting unit 180according to the selection signal Select.

Although in the example of FIG. 2, the imaging region 131 having thesingle photoelectric converting unit 104 is shown, a plurality ofphotoelectric converting units 104 may be provided in the imaging region131. If a plurality of photoelectric converting units 104 is provided inthe imaging region 131, the corresponding AD converting unit 180sequentially reads out analog signals according to electrical chargesstored in the respective photoelectric converting units 104.

The AD converting unit 180 has a level comparator 184 and a periodmeasuring unit 186. The level comparator 184 compares the level of aramp signal input from the corresponding ramp generating unit 182, andthe level of a pixel signal from the corresponding imaging region 131.For example, the level comparator 184 outputs a logical value 0 during aperiod in which the level of a pixel signal is lower than the level of aramp signal, and outputs a logical value 1 during a period in which thelevel of a pixel signal is equal to or higher than the level of a rampsignal.

The period measuring unit 186 measures a period from the timing when theramp generating unit 182 started inputting a ramp signal to the levelcomparator 184 until the level comparator 184 outputs a logical value 1.The period measuring unit 186 may be a counter that receives a clocksignal at a predetermined frequency, and counts the pulse count of theclock signal within the period. The period measuring unit 186 outputs adigital value according to the measured length of the period. As oneexample, the period measuring unit 186 outputs, as a digital value, thepulse count of a clock signal counted within the period.

According to the AD converting unit 180 in the present example, theperiod from the timing when the ramp generating unit 182 startedinputting a ramp signal to the level comparator 184 until the levelcomparator 184 outputs a logical value 1 changes depending on theinclination of the ramp signal. For this reason, the gain in the ADconverting unit 180 can be controlled based on the inclination of a rampsignal.

FIG. 3 is a timing diagram showing an operation example of the firstimaging region 131-1 and the second imaging region 131-2. In the presentexample, ramp signals with different inclinations are used for the firstimaging region 131-1 and the second imaging region 131-2.

In FIG. 3, ADC1 input indicates the waveform of a first pixel signalinput to the first AD converting unit 180-1, Ramp 1 indicates thewaveform of a first ramp signal generated by the first ramp generatingunit 182-1, and ADC1 out indicates, with the length along the time axis,the magnitude of a digital value output by the first AD converting unit180-1. Similarly, ADC2 input indicates the waveform of a second pixelsignal input to the second AD converting unit 180-2, Ramp2 indicates thewaveform of a second ramp signal generated by the second ramp generatingunit 182-2, and ADC2 out indicates, with the length along the time axis,the magnitude of a digital value output by the second AD converting unit180-2.

In the present example, the waveforms of the first pixel signal and thesecond pixel signal are the same for the sake of comparison. Also, theimage sensor 100 according to the present example performs so-calledcorrelated double sampling CDS. Upon reception by the reset transistor154 of a reset signal at the H level, electrical charges stored by therespective photoelectric converting units 104 are reset, and the levelsof pixel signals input to the respective AD converting units 180 becomea predetermined reference level.

In a state where the levels of pixel signals are stable, the respectiveramp generating units 182 generate ramp signals. The initial level of aramp signal in the present example is higher than the reference level ofa pixel signal, and the level decreases at a certain ratio as timeelapses. The AD converting unit 180 measures a period from the timingwhen the level of a ramp signal starts lowering until the timing whenthe level of the ramp signal becomes lower than the level of a pixelsignal. Thereby, the AD converting unit 180 outputs a digital valueindicating the reference level of the pixel signal.

Next, upon reception by the transfer transistor 152 of the transfersignal Tx, a pixel signal according to the amount of electrical chargesstored by the photoelectric converting unit 104 is input to the ADconverting unit 180. In a state where the level of a pixel signal isstable, the ramp generating unit 182 generates a ramp signal. The ADconverting unit 180 measures a period from the timing when the level ofa ramp signal starts lowering until the timing when the level of theramp signal becomes lower than the level of a pixel signal. Thereby, theAD converting unit 180 outputs a digital value indicating the level ofthe pixel signal. Based on the difference between the level and thereference level, the luminance value of a pixel of the photoelectricconverting unit 104 is calculated.

As described above, in the present example, ramp signals with differentinclinations are used for the first imaging region 131-1 and the secondimaging region 131-2. For this reason, as shown in FIG. 3, even if thewaveforms of pixel signals are the same, the values of digital imagesignals output are different. For example, the larger the inclination ofthe waveform of a ramp signal, the smaller the value of a digital imagesignal. In this manner, by independently controlling the inclinations ofrespective ramp signals, the gain between the input and the output ineach AD converting unit 180 can be controlled.

The respective ramp generating units 182 may generate ramp signals withdifferent inclinations according to differences in the sensitivity ofthe corresponding photoelectric converting units 104. Here, sensitivitymeans the gain in the level of a pixel signal relative to the intensityof incident light. Also, sensitivity may mean the gain in the level of apixel signal relative to the intensity in a particular wavelengthcomponent of incident light.

FIG. 4 is a figure showing an example of the plurality of imagingregions 131. In the present example, the first imaging region 131-1 hasa plurality of first photoelectric converting units 104-1, and thesecond imaging region 131-2 has a plurality of second photoelectricconverting units 104-2. It should be noted that although in FIG. 4, onlytwo imaging regions 131 are illustrated, a larger number of imagingregions 131 are included in the imaging unit 120. The respectivephotoelectric converting units 104 are included in any of the imagingregions 131. It should be noted that the respective transistors shown inFIG. 2 are provided to the respective photoelectric converting units104.

The first photoelectric converting units 104-1 are photoelectricconverting units for focus detection that detect focus positions of anoptical system through which incident light has passed. Signals outputby the first photoelectric converting units 104-1 are used for otherpurposes than focus detection, and also as pixel signals to configure animage. The second photoelectric converting units 104-2 are photoelectricconverting unit not for focus detection.

In general, the sensitivity of the first photoelectric converting units104-1 for focus detection is different from the sensitivity of the othersecond photoelectric converting units 104-2. For example, the firstphotoelectric converting units 104-1 have light-shielding portions 122that shield halves of light-receiving surfaces from light. That is, thesensitivity of the first photoelectric converting units 104-1 is in somecases about half of that of the other second photoelectric convertingunits 104-2. The first ramp generating unit 182-1 generates a rampsignal to compensate for a decrease in the sensitivity. For example, thefirst ramp generating unit 182-1 generates a ramp signal whoseinclination is half of that of the second ramp signal. Thereby, the gainin the first AD converting unit 180-1 is twice the gain in the second ADconverting unit 180-2, and the difference in the sensitivity between thefirst photoelectric converting units 104-1 and the second photoelectricconverting units 104-2 can be compensated for.

FIG. 5 is a figure showing another example of the plurality of imagingregions 131. The imaging unit 120 according to the present example hasthree imaging regions 131. In FIG. 5, one or two photoelectricconverting units 104 included in the respective imaging regions 131 areshown, and the configuration of the entire imaging regions 131 isomitted. The first photoelectric converting units 104-1 included infirst imaging regions 131-1 convert first wavelength components inincident light into first pixel signals. The second photoelectricconverting unit 104-2 included in a second imaging region 131-2 convertssecond wavelength components, which are in incident light and aredifferent from the first wavelength components, into second pixelsignals. A third photoelectric converting unit 104-3 included in a thirdimaging region 131-3 converts third wavelength components, which are inincident light and are different from the first wavelength componentsand the second wavelength components, into third pixel signals. In thepresent example, the first wavelength components are componentscorresponding to green, the second wavelength components are componentscorresponding to blue, and the third wavelength components are componentcorresponding to red. The respective photoelectric converting units 104may have color filters that allow passage of predetermined wavelengthcomponents therethrough.

Because the respective photoelectric converting units 104 convertincident light that has passed color filters or the like havingdifferent characteristics into pixel signals, the sensitivities of pixelsignals for incident light before passage through color filters or thelike are not necessarily the same. The respective ramp generating units182 generate ramp signals having inclinations according to thesensitivities of the corresponding photoelectric converting units 104.Thereby, differences in the sensitivities of the respectivephotoelectric converting units 104 can be compensated for.

It should be noted that the ramp generating units 182 may be provided tobe shared by a plurality of imaging regions 131 having the samesensitivity. For example, the image sensor 100 may comprise three rampgenerating units 182 corresponding to respective colors of green, blueand red, and the respective ramp generating units 182 may feed rampsignals to one or more AD converting units 180 corresponding to one ormore imaging regions 131 corresponding to the respective colors. Also,the image sensor 100 may further comprise the ramp generating unit 182corresponding to the imaging region 131 for focus detection shown inFIG. 4.

FIG. 6 is a figure showing another example of the plurality of imagingregions 131. The ramp generating unit 182 in the present examplecontrols the inclination of a ramp signal according to the position of acorresponding imaging region 131. For example, the ramp generating unit182 may control the inclination of a ramp signal according to thedistance from the center of the entire imaging region. By performingcontrol in such a manner, even if variation occurs in the incident lightamounts according to the positions of the imaging regions 131 because ofcharacteristics of an optical system, the level differences of pixelsignals due to the variation can be compensated for. Inclinations oframp signals to be adopted for the respective imaging regions 131 may bedetermined based on the levels of pixel signals output by the respectiveimaging regions 131 when known reference light is incident thereon.

FIG. 7 is a figure showing a configuration example of the imaging unit120 and the plurality of AD converting units 180. It should be notedthat although in FIG. 7, ramp generating units 182 are omitted, an ADconverting unit 180 and a ramp generating unit 182 are provided in aone-to-one correspondence.

The imaging unit 120 has a plurality of photoelectric converting units104 arranged in a matrix form. The imaging unit 120 according to thepresent example has N photoelectric converting units 104 in the columndirection and M photoelectric converting units 104 in the row direction.Also, in the present example, the P×M AD converting units 180 areprovided. It should be noted that P is a divisor of N, and in theexample of FIG. 7, P=4.

In the present example, each of the imaging regions 131 includes N/Pphotoelectric converting units 104. An AD converting unit 180 and animaging region 131 correspond to each other in a one-to-onecorrespondence. That is, each of the AD converting units 180 is providedcorresponding to N/P photoelectric converting units 104, andsequentially reads out pixel signals of corresponding photoelectricconverting units 104. In the present example, four AD converting units180 are provided in each column. The respective AD converting units 180are connected to every three other photoelectric converting units 104 inthe corresponding column.

For example, the first AD converting unit 180-1 is connected to thefirst, fifth, ninth, n-th, (n+4)-th, . . . , (N−3)-th photoelectricconverting units 104 in the corresponding column. Similarly, the secondAD converting unit 180-2 is connected to the second, sixth, tenth,(n+1)-th, (n+5)-th, . . . , (N−2)-th photoelectric converting units 104in the corresponding column. The third AD converting unit 180-3 isconnected to the third, seventh, eleventh, (n+2)-th, (n+6)-th, . . . ,(N−1)-th photoelectric converting units 104 in the corresponding column,and the fourth AD converting unit 180-4 is connected to the fourth,eighth, twelfth, (n+3)-th, (n+7)-th, . . . , N-th photoelectricconverting units 104 in the corresponding column.

It should be noted that in the example shown in FIG. 7, the plurality ofAD converting units 180 and the plurality of ramp generating units 182are provided, in the imaging unit 120, on the same plane as theplurality of photoelectric converting units 104. P AD converting units180 provided in the same column may read out pixel signals at the sametiming, or can read out pixel signals at different timing.

FIG. 8 is a timing diagram showing an operation example of four ADconverting units 180 provided in the same column. In the presentexample, four pixel signals of photoelectric converting units 104 in thesame column are read out at once simultaneously. In FIG. 8, Selectxindicates the number of a photoelectric converting unit 104 that inputsa pixel signal to the x-th AD converting unit 180.

The respective photoelectric converting units 104 receive the same resetsignal Reset. The cycle of the reset signal Reset is, in one example, 2to 20 μs. Then, the n-th, (n+1)-th, (n+2)-th and (n+3)-th photoelectricconverting units 104 receive transfer signals Tx at the same timing.Also, as photoelectric converting units 104 that should read out pixelsignals, the n-th, (n+1)-th, (+2)-th and (n+3)-th photoelectricconverting units 104 are selected simultaneously by a select signalSelect. The respective AD converting units 180 simultaneously read outpixel signals of the selected photoelectric converting units 104.

Then, according to the next reset signal Reset, pixel signals of the(n+4)-th, (+5)-th, (n+6)-th and (n+7)-th photoelectric converting units104 are read out simultaneously in a similar procedure. With suchoperation, pixel signals of P (four in the example of FIG. 8)photoelectric converting units 104 are read out simultaneously everypredetermined cycle (for example, 2 to 20 μs). For this reason, if pixelsignals of photoelectric converting units 104 in each column are readout in a rolling scheme, differences in the timing of readout equal thecycle of the reset signal Reset.

FIG. 9 is a timing diagram showing details of an operation of the firstAD converting unit 180-1 and the second AD converting unit 180-2 in theoperation example shown in FIG. 8. It should be noted that in thepresent example, similar to the example shown in FIG. 3, theinclinations of the first ramp signal Ramp1 and the second ramp signalRamp2 are different from each other. As explained with reference to FIG.3, the gains of the first AD converting unit 180-1 and the second ADconverting unit 180-2 are different according to the inclinations oframp signals. It should be noted that, as explained with reference toFIG. 8, operation timing of the first AD converting unit 180-1 and thesecond AD converting unit 180-2 are the same.

FIG. 10 is a timing diagram showing another operation example of four ADconverting units 180 provided in the same column. In the presentexample, the timing of readout of four AD converting units 180 isstaggered by ΔT. Specifically, the timing of readout of the respectiveAD converting units 180 is staggered by the cycle of reset signals (forexample, 2 to 20 μs) divided by P. In the present example, the shift ΔTin the timing of readout=2 to 20 μs/4=0.5 to 5 μs.

In the present example, the phases of reset signals input to therespective photoelectric converting units 104 are staggered by ΔT. Also,the phases of transfer signals Tx and selection signals Select input tothe respective photoelectric converting units 104 are staggered by ΔT.Also, the timing of readout of AD converting units 180 is staggered byΔT.

FIG. 11 is a timing diagram showing details of an operation of the firstAD converting unit 180-1 and the third AD converting unit 180-3 in theoperation example shown in FIG. 10. It should be noted that in thepresent example, similar to the example shown in FIG. 3, theinclinations of the first ramp signal Ramp1 and the third ramp signalRamp3 are different from each other.

Also, in order for the timing of readout of the AD converting units 180to be staggered by ΔT, the timing at which the respective rampgenerating units 182 generate ramp signals is staggered by ΔT. That is,the timing of a first ramp signal Ramp1 and a third ramp signal Ramp3 isstaggered by 2×ΔT. The timing at which the respective ramp generatingunits 182 generate ramp signals is, for example, timing that is delayedfrom a corresponding reset signal Reset by a predetermined delay amount.

As shown in FIG. 10 and FIG. 11, by causing the timing of ramp signalsto be staggered, differences in the timing of readout at which pixelsignals are read out in a rolling scheme can be made 1/P-fold incomparison to that in the example shown in FIG. 8 and FIG. 9. For thisreason, an image with less distortion can be obtained.

FIG. 12 is a figure showing an image of differences in the timing ofreadout in rolling readout. The top portion of FIG. 12 shows differencesin the timing of readout in the example shown in FIG. 8 and FIG. 9, andthe bottom portion shows differences in the timing of readout in theexample shown in FIG. 10 and FIG. 11.

In FIG. 12, the left edges in the row direction indicate the timing ofreadout of photoelectric converting units 104 in respective rows. Thatis, steps in the row direction indicate timing differences. As describedabove, by causing the timing of ramp signals in the ramp generatingunits 182 to be staggered, differences in the timing of readout can bemade 1/P-fold.

FIG. 13A is a figure showing a configuration example of a plurality oframp generating units 182. In the present example, the image sensor 100has a seed ramp generating unit 190 and a plurality of ramp generatingunits 182 a. The seed ramp generating unit 190 generates seed rampsignals with a predetermined inclination. In the present example, therespective ramp generating units 182 a amplifiers that receive seed rampsignals after being branched, and amplify and output the seed rampsignals. Amplification factors in the respective ramp generating units182 a can be controlled independently. Thereby, the respective rampgenerating units 182 a can generate ramp signals with inclinationsaccording to the amplification factors.

Also, the respective ramp generating units 182 a may further have delayvariable elements that delay seed ramp signals. Thereby, the respectiveramp generating unit 182 a can independently control the timing of rampsignals.

FIG. 13B is a figure showing another configuration example of theplurality of ramp generating units 182. In the present example, theimage sensor 100 has a clock generating unit 192, a plurality of rampgenerating units 182 b, and a ramp control unit 188. The clockgenerating unit 192 generates a clock signal at a predeterminedfrequency. In the present example, the respective ramp generating units182 b have DA converters that output, at the frequency of the clocksignal, digital signals given from the ramp control unit 188. The rampcontrol unit 188 sequentially inputs, to the ramp generating units 182b, digital values whose values change at a predetermined inclination,and causes the ramp generating units 182 b to output ramp signals.

The ramp control unit 188 can cause ramp signals with differentinclinations to be output by independently controlling the inclinationsof digital values for each ramp generating unit 182 b. Also, the rampcontrol unit 188 can cause ramp signals of different start timing to beoutput by independently controlling the timing to input digital valuesfor each ramp generating unit 182 b.

FIG. 14 is a cross-sectional view of the image sensor 100 according tothe present embodiment. Although in the present example, a so-calledbackside irradiation-type image sensor 100 is shown, but the imagesensor 100 is not limited to the backside irradiation-type, but may be afront side irradiation-type. The image sensor 100 only has to have astructure comprising a laminate chip stacked on the imaging chip 113.

The image sensor 100 according to the present example comprises theimaging chip 113 that outputs a pixel signal corresponding to incidentlight, the signal processing chip 111 that processes the pixel signal,and a memory chip 112 that stores a digital image signal. These imagingchip 113, signal processing chip 111 and memory chip 112 are stacked oneach other, and are electrically connected with each other by aplurality of electrically conductive bumps 109 such as Cu. In thepresent example, the signal processing chip 111 and the memory chip 112are equivalent to the above-mentioned laminate chip.

It should be noted that as illustrated, incident light is incidentmainly in the positive Z-axis direction indicated by an outline arrow.In the present embodiment, the surface of the imaging chip 113 on whichthe incident light is incident is called a backside. Also, as shown inthe coordinate axes, the rightward direction on the sheet that isorthogonal to the Z-axis is defined as the positive X-axis direction,and the direction toward readers on the sheet that is orthogonal to theZ-axis and the X-axis is defined as the positive Y-axis direction.

One example of the imaging chip 113 is a backside irradiation-type MOSimage sensor. The imaging chip 113 corresponds to the imaging unit 120shown in FIG. 1 to FIG. 13B. A PD layer 106 is disposed on the rearsurface side of a wiring layer 108. The PD layer 106 has a plurality ofthe photoelectric converting units 104 that generate electrical chargesaccording to light. The imaging chip 113 outputs pixel signals accordingto the electrical charges. The PD layer 106 according to the presentexample has the plurality of photoelectric converting units 104 disposedtwo-dimensionally, and transistors 105 that are provided correspondingto the photoelectric converting units 104. The transistors 105correspond to the respective transistors in FIG. 2 or other figures.

The side of the PD layer 106 on which incident light is incident isprovided with color filters 102 with a passivation film 103 interposedtherebetween. There are multiple types of the color filters 102 thatallow passage of light of mutually different wavelength regions, and thecolor filters 102 are arrayed in specific manners corresponding to therespective photoelectric converting units 104. A set of a color filter102, a photoelectric converting unit 104 and a transistor 105 forms onepixel.

The side of the color filter 102 on which incident light is incident isprovided with microlenses 101 corresponding to respective pixels. Themicrolenses 101 concentrate incident light toward correspondingphotoelectric converting units 104.

The wiring layer 108 has a wire 107 that transmits pixel signals fromthe PD layer 106 to the signal processing chip 111. The wire 107 may bemultilayered, and may be provided with an active element or a passiveelement.

A plurality of the bumps 109 are disposed on the front surface of thewiring layer 108. The plurality of bumps 109 are aligned with aplurality of the bumps 109 provided on an opposite surface of the signalprocessing chip 111, and the imaging chip 113 and the signal processingchip 111 are pressurized for example; thereby, the aligned bumps 109 arejoined and electrically connected with each other.

Similarly, a plurality of the bumps 109 are disposed on mutuallyopposite surfaces of the signal processing chip 111 and the memory chip112. These bumps 109 are aligned with each other, and the signalprocessing chip 111 and the memory chip 112 are pressurized for example;thereby, the aligned bumps 109 are joined and electrically connectedwith each other.

It should be noted that the bumps 109 may be joined with each other notonly by Cu bump joining by solid phase diffusion, but also by micro bumpcoupling by solder melting. Also, one bump 109 or a plurality of bumps109 may be provided to one output wire described below, for example.Accordingly, the size of the bumps 109 may be larger than the pitch ofthe photoelectric converting units 104. Also, in a peripheral regionother than a pixel region in which pixels are arrayed, bumps larger thanthe bumps 109 corresponding to the pixel region may be provided as well.

The signal processing chip 111 receives analog pixel signals output bythe imaging chip 113. The signal processing chip 111 performspredetermined signal processing on the received pixel signals, andoutputs the processed pixel signals to the memory chip 112. The memorychip 112 stores the signals received from the signal processing chip111.

The signal processing chip 111 according to the present example isprovided with the plurality of AD converting units 180 and the pluralityof ramp generating units 182. The signal processing chip 111 may performpredetermined operation such as correction on the digital image signals.

At least some of the plurality of AD converting units 180 are arrangedin two dimensions on an ADC arrangement plane that is parallel to aplane on which a plurality of pixels are provided. For example, in theimaging chip 113, a plurality of pixels are arranged in two dimensionsalong the row direction and the column direction, and in the signalprocessing chip 111, the plurality of AD converting units 180 arearranged in two dimensions along the row direction and the columndirection. The plurality of AD converting units 180 are preferablyarranged at constant intervals in the signal processing chip 111. Also,the plurality of AD converting units 180 may be non-uniformly arrangedon the ADC arrangement plane of the signal processing chip 111. Forexample, the plurality of AD converting units 180 may be arranged suchthat the density of them becomes higher at edge portions of the ADCarrangement plane of the signal processing chip 111 than at the centerthereof.

Also, the plurality of AD converting units 180 may be arranged, in thesignal processing chip 111, on a plurality of ADC arrangement planeswhose positions in the Z-axis direction are different. That is, thesignal processing chip 111 may be a multilayered chip, and the pluralityof AD converting units 180 may be provided in different layers. In thiscase also, if the positions at which the plurality of AD convertingunits 180 are arranged are projected onto a single ADC arrangementplane, the respective AD converting units 180 are preferably arranged atconstant intervals.

Also, the signal processing chip 111 has a TSV (through-silicon via) 110connecting, with each other, circuits respectively provided to the frontand rear surfaces. The TSV 110 is preferably provided in a peripheralregion. Also, the TSV 110 may also be provided to a peripheral region ofthe imaging chip 113 and the memory chip 112.

FIG. 15 is a block diagram illustrating a configuration example of animaging apparatus 500 according to an implementation example. Theimaging apparatus 500 comprises an imaging lens 520 as an imagingoptical system, and the imaging lens 520 guides a subject light fluxthat is incident along an optical axis OA to the image sensor 100. Theimaging lens 520 may be a replaceable lens that can be attached to anddetached from the imaging apparatus 500. The imaging apparatus 500mainly comprises the image sensor 100, a system control unit 501, adrive unit 502, a photometry unit 503, a work memory 504, a recordingunit 505 and a display unit 506.

The imaging lens 520 is configured with a plurality of groups of opticallenses, and forms, near its focal plane, an image of a subject lightflux from a scene. It should be noted that in FIG. 15, the imaging lens520 is expressed by a single virtual representative lens arranged nearthe pupil. The drive unit 502 is a control circuit that performselectrical charge storage control such as timing control, region controlor the like of the imaging unit 120 according to an instruction from thesystem control unit 501. The drive unit 502 and the system control unit501 in the present example may serve the functions of the AD convertingunit 180 explained with reference to FIG. 1 to FIG. 13B. As shown inFIG. 14, part of the control circuit that forms the drive unit 502 andthe system control unit 501 may be formed as a chip, and stacked on theimaging chip 113.

The image sensor 100 passes a pixel signal to the image processing unit511 of the system control unit 501. The image sensor 110 is the same asthe image sensor 100 explained with reference to FIG. 1 to FIG. 13B. Theimage processing unit 511 performs various image processing by using thework memory 504 as a work space, and generates image data. For example,if image data in a JPEG file format is to be generated, the imageprocessing unit 511 performs white balancing, gamma processing, or thelike, and then performs a compression process. Generated image data isrecorded in the recording unit 505, and is converted into a displaysignal to be displayed on the display unit 506 for a preset length oftime.

The photometry unit 503 detects the luminance distribution of a sceneprior to a series of image-capturing sequences to generate image data.The photometry unit 503 includes an AE sensor of about one millionpixels, for example. The operating unit 512 of the system control unit501 receives an output of the photometry unit 503 to calculate theluminance of each region of a scene. The operating unit 512 determinesthe shutter speed, diaphragm value, ISO speed according to thecalculated luminance distribution. It should be noted that pixels usedin the above-mentioned AE sensor may be provided within the imaging unit120, and in this case a photometry unit 503 separate from the imagingunit 120 may not be provided.

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

The operations, procedures, steps, and stages of each process performedby an apparatus, system, program, and method shown in the claims,embodiments, or diagrams can be performed in any order as long as theorder is not indicated by “prior to,” “before,” or the like and as longas the output from a previous process is not used in a later process.Even if the process flow is described using phrases such as “first” or“next” in the claims, embodiments, or diagrams, it does not necessarilymean that the process must be performed in this order.

What is claimed is:
 1. An electronic device comprising: an image sensorthat includes a first photoelectric converting section that convertslight into electrical charge, a second photoelectric converting sectionthat converts light into electrical charge, a first signal line, towhich a first signal based on electrical charge of the firstphotoelectric converting section is output, and a second signal line, towhich a second signal based on electrical charge of the secondphotoelectric converting section is output; and a control section thatperforms control in a manner such that, after starting to storeelectrical charge converted by the first photoelectric convertingsection, storing electrical charge in the second photoelectricconverting section is started, and that, before terminating output ofthe first signal to the first signal line, output of the second signalto the second signal line is terminated.
 2. The electronic deviceaccording to claim 1, wherein the image sensor includes a first transfergate that transfer electrical charge of the first photoelectricconverting section, a second transfer gate that transfer electricalcharge of the second photoelectric converting section, a first transfercontrol line, to which a first transfer control signal for controllingthe first transfer gate is output, that is connected to the firsttransfer gate, and a second transfer control line, to which a secondtransfer control signal for controlling the second transfer gate isoutput, that is connected to the second transfer gate, and the controlsection further performs control in a manner such that, beforeoutputting the first transfer control signal to the first transfercontrol line, the second transfer control signal is output to the secondtransfer control line.
 3. The electronic device according to claim 2,wherein the image sensor includes a first reset section that resets apotential of a first floating diffusion to which electrical charge fromthe first photoelectric converting section is transferred by the firsttransfer gate, a second reset section that resets a potential of asecond floating diffusion to which electrical charge from the secondphotoelectric converting section is transferred by the second transfergate, a first reset control line, to which a first reset control signalfor controlling the first rest section is output, and that is connectedto the first reset section, a second reset control line, to which asecond reset control signal for controlling the second rest section isoutput, and that is connected to the second reset section, and thecontrol section further performs control in a manner such that, beforeoutputting the second reset control signal to the second reset controlline, the first reset control signal is output to the first resetcontrol line.
 4. The electronic device according to claim 3, wherein theimage sensor includes a first selection section that outputs the firstsignal to the first signal line, a second selection section that outputsthe second signal to the second signal line, a first selection controlline, to which a first selection control signal for controlling thefirst selection unit is output, that is connected to the first selectionunit, and a second selection control line, to which a second selectioncontrol signal for controlling the second selection unit is output, thatis connected to the second selection unit, and the control sectionfurther performs control in a manner such that, before outputting thefirst selection control signal to the first selection control line, thesecond selection control signal is output to the second selectioncontrol line.
 5. The electronic device according to claim 1, wherein theimage sensor includes a first reset section that resets a potential of afirst floating diffusion to which electrical charge from the firstphotoelectric converting section is transferred, a second reset sectionthat resets a potential of a second floating diffusion to whichelectrical charge from the second photoelectric converting section istransferred, a first reset control line, to which a first reset controlsignal for controlling the first rest section is output, and that, isconnected to the first reset section, a second reset control line, towhich a second reset control signal for controlling the second restsection is output, and that is connected to the second reset section,and the control section further performs control in a manner such that,before outputting the second reset control signal to the second resetcontrol line, the first reset control signal is output to the firstreset control line.
 6. The electronic device according to claim 5,wherein the image sensor includes a first selection section that outputsthe first signal to the first signal line, a second selection sectionthat outputs the second signal to the second signal line, a firstselection control line, to which a first selection control signal forcontrolling the first selection unit is output, that is connected to thefirst selection unit, and a second selection control line, to which asecond selection control signal for controlling the second selectionunit is output, that is connected to the second selection unit, and thecontrol section further performs control in a manner such that, beforeoutputting the first selection control signal to the first selectioncontrol line, the second selection control signal is output to thesecond selection control line.
 7. The electronic device according toclaim 1, wherein the image sensor includes a first selection sectionthat outputs the first signal to the first signal line. a secondselection section that outputs the second signal to the second signalline, a first selection control line, to which a first selection controlsignal for controlling the first selection unit is output, that isconnected to the first selection unit, and a second selection controlline, to which a second selection control signal for controlling thesecond selection unit is output, that is connected to the secondselection unit, and the control section further performs control in amanner such that, before outputting the first selection control signalto the first selection control line, the second selection control signalis output to the second selection control line.
 8. The electronic deviceaccording to claim 1, wherein the image sensor includes a first signalprocessing section that performs a signal processing to the first signaloutput to the first signal line, and a second signal processing sectionthat performs a signal processing to the second signal output to thesecond signal line.
 9. The electronic device according to claim 8,wherein the first signal processing section includes at least a part ofa first amplifier circuit for amplifying the first signal, and thesecond signal processing section includes at least a part of a secondamplifier circuit for amplifying the second signal.
 10. The electronicdevice according to claim 8, wherein the first signal processing sectionincludes a first conversion circuit that is used for converting thefirst signal into a digital signal, and the second signal processingsection includes a second conversion circuit that is used for convertingthe second signal into a digital signal.
 11. The electronic deviceaccording to claim 10, wherein the image sensor includes a first supplyline, to which a first ramp signal is supplied, that is connected to thefirst conversion circuit, and a second supply line, to which a secondramp signal is supplied, that is connected to the second conversioncircuit, the second ramp signal having an inclination that is differentfrom an inclination of the first ramp signal.
 12. The electronic deviceaccording to claim 11, wherein the control section performs a control ina manner such that a timing of output of the first ramp signal to thefirst supply line is different from a timing of output of the secondramp signal to the second supply line.
 13. The electronic deviceaccording to claim 10, wherein the image sensor includes an image chipthat includes the first photoelectric converting section and the secondphotoelectric converting section, and a signal processing chip thatincludes at least a part of the first conversion circuit and at least apart of the second conversion circuit.
 14. The electronic deviceaccording to claim 13, wherein the image chip is stacked on the signalprocessing chip.
 15. The electronic device according to claim 10,wherein the image sensor includes a first storing section that storesthe first signal converted into a digital signal using the firstconversion circuit, and a second storing section that stores the secondsignal converted into a digital signal using the second conversioncircuit.
 16. The electronic device according to claim 15, wherein theimage sensor includes an image chip that includes the firstphotoelectric converting section and the second photoelectric convertingsection, a signal processing chip that includes at least a part of thefirst conversion circuit and at least a part of the second conversioncircuit, and a memory chip that includes the first storing section andthe second storing section.
 17. The electronic device according to claim16, wherein the image chip is stacked on the memory chip.
 18. Theelectronic device according to claim 1, wherein a plurality of the firstphotoelectric converting sections are arranged in a first region towhich light is incident, a plurality of the second photoelectricconverting sections are arranged in a second region to which light isincident, each first signal based on electrical charge of acorresponding first photoelectric converting section is output to thefirst signal line, and each second signal based on electrical charge ofa corresponding second photoelectric converting section is output to thesecond signal line.
 19. The electronic device according to claim 18,wherein the plurality of first photoelectric converting sections arearranged side by side in a first direction, and the plurality of secondphotoelectric converting sections are arranged side by side in the firstdirection.
 20. The electronic device according to claim 19, wherein theplurality of first photoelectric converting sections are arranged sideby side in a second direction that intersects with the first direction,and the plurality of second photoelectric converting sections arearranged side by side in the second direction.